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FACULTY OF SCIENCE AND TECHNOLOGY
MASTER’S THESIS
Study programme/specialization:
Petroleum Engineering/ Drilling Technology
Spring semester, 2018 Open
Author: Kim Huy Nguyen
………..
(Signature of author)
Programme coordinator:
Supervisor(s): Mesfin Belayneh.
Title of master’s thesis:
Effect of 15nm SiO2 Nanoparticles on Enhanced Oil Recovery and Drilling Fluid:
Experimental and Simulation studies Credits: 30
Keywords:
Drilling fluid EOR
Silica nanoparticle (SiO2) Rheological properties Tribology
Viscoelasticity IFT
Contact angle
Number of pages: 101
+ Supplemental material/other: 18
Stavanger, 15 – 06 – 2018
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ACKNOWLEDGEMENTS
First of all, I would like to give my deepest appreciation for the invaluable guidance from my supervisor of this thesis, Professor Mesfin Belayneh from the University of Stavanger.
As the supervisor, he encouraged me to fulfil the project about improving oil recovery, as well as he personally and economically invested to allow the core flooding experiments to be executed at IRIS. Throughout the whole period of writing the thesis he was always available at the office, and even joined and advised the laboratory work.
At the occasion, I would also show my gratitude for the assistance and the cooperation to John Zuta at IRIS which supported me during the flooding of the sandstone core plugs.
Finally, I will thank the University of Stavanger to be able to use the laboratory and the associated equipment that has been presented and utilized for the experimental part of the thesis, as well as the necessary materials.
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ABSTRACT
Nanotechnology is among the most remarkable technology in the modern science, and due to unique and unrevealed abilities the tiny size of particles possesses, this technology has also been questioned in order to be worthy. The implementations of nanotechnology have already been used in diverse industries, yet to be a part of the oil and gas industry. The lack of investigations, and trust may be the reason for not applying the technology to the current ordinary technologies and techniques.
However, there are numerous optimistic scientists who suggest integrating the nanoparticles as a part of either formulating the drilling fluids and cement, or the enhanced oil recovery, as the nanotechnology shows promising potential.
During the thesis, nanofluids of different SiO2 concentrations were studied to influence in EOR to raise the recovery factor and the performance of the drilling fluids in terms of rheology and the desired functions. The following points present the highlighted observations:
• 0.075 wt.% SiO2 NF gave the best value as reducing the IFT by 14,44% and increased the contact angle by 52,3% to change the wettability to water – wet.
• 0.050 wt.% SiO2 NF gave an incremental of 2,42% in a tertiary recovery method, while 0.075 wt.% SiO2 NF did not alter the recovery factor.
• PV and ECD was not found to be any noteworthy influenced by adding nanoparticles.
• Additional 6.20% extended drilling was achieved by using CMC + 0.025g SiO2 DF in WellPlan.
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TABLE OF CONTENT
ACKNOWLEDGEMENTS ... 2
ABSTRACT ... 3
LIST OF FIGURES ... 7
LIST OF TABLES ... 9
NOMENCLATURE... 10
1. INTRODUCTION ... 11
1.1. BACKGROUND & MOTIVATION ... 11
1.1.1. ENHANCED OIL RECOVERY ... 12
1.1.2. DRILLING FLUID ... 13
1.2. FORMULATION OF THE PROBLEM ... 14
1.3. OBJECTIVE ... 15
1.4. METHOD OF RESEARCH ... 15
2. LITERATURE STUDY ... 17
2.1. NANOTECHNOLOGY ... 17
2.2. APPLICATIONS OF NANOTECHNOLOGY... 18
3. THEORY ... 24
3.1 RHEOLOGY ... 24
3.2 RHEOLOGICAL MODELS ... 26
3.2.1 NEWTONIAN FLUIDS ... 26
3.2.2 NON – NEWTONIAN FLUIDS ... 26
3.3 VISCOELASTICITY ... 29
3.3.1. OSCILLATORY AMPLITUDE SWEEP TEST ... 32
3.4 TORQUE & DRAG ... 33
3.5 HYDRAULICS ... 35
3.6 ROCK FLUID PROPERTIES ... 37
3.6.1 POROSITY ... 37
3.6.2 PERMEABILITY ... 38
3.6.3 RELATIVELY PERMEABILITY ... 38
3.6.4 CONTACT ANGLE & WETTABILITY ... 39
3.6.5 CAPILLARY PRESSURE ... 41
4. ADDITIVES USED IN THIS THESIS WORK ... 43
4.1 BENTONITE ... 43
4.1.1. FLOCCULATED SYSTEM ... 46
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4.1.2 DEFLOCCULATED SYSTEM ... 47
4.1.3 AGGREGATED SYSTEM ... 47
4.1.4 DISPERSED SYSTEM ... 48
4.2 CMC – Carboxymethyl Cellulose... 48
4.3 DUOVIS ... 49
4.3 KCl – Potassium Chloride ... 49
4.4 SEAWATER ... 50
4.5 OIL ... 50
4.6 NANOPARTICLES ... 51
4.7 EOR MECHANISMS ... 53
4.7.1 IFT REDUCTION ... 53
4.7.2 WETTABILITY ALTERATION ... 54
4.7.3 REDUCED MOBILITY RATIO ... 54
4.7.4 DISJOINING PRESSURE ... 55
5. EXPERIMENTAL WORK ... 56
5.1 IMPACT OF NANO - SiO2 in EOR ... 56
5.1.1 PREPARATION OF SILICA NANOFLUIDS ... 56
5.1.2 DENSITY & VISCOSITY OF SiO2 NANOFLUIDS ... 58
5.1.3 EFFECT OF SiO2 NANOFLUIDS ON INTERFACIAL TENSION ... 58
5.1.3 EFFECT OF SILICA NANOFLUIDS ON CONTACT ANGLE ... 62
5.1.4 CORE FLOODING ... 65
5.2 IMPACT OF NANO - SiO2 in DRILLING FLUIDS ... 69
5.2.1 INFLUENCE OF SILICA IN CMC DF ... 69
5.2.2 INFLUENCE OF SILICA ON DUOVIS DF ... 74
5.2.3 MEASUREMENTS OF VISCOELASTICITY ... 78
6 PERFORMANCE OF SIMULATION ... 82
6.1 RHEOLOGICAL MODELS ... 82
6.1.1 REFERENCE CMC SYSTEM ... 82
6.1.2 CMC + 0.025 SiO2 SYSTEM ... 83
6.1.3 REFERENCE DUOVIS SYSTEM ... 84
6.1.4 DUOVIS + 0.050g SiO2 SYSTEM ... 85
6.1.5 COMPARISON of RHEOLOGICAL MODELS ... 86
6.2 SIMULATION OF HYDRAULICS ... 88
6.3 SIMULATION OF TORQUE AND DRAG ... 91
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7 SUMMARY & DISCUSSIONS ... 94
7.1 DISCUSSION OF LITERATURE STUDY... 94
7.2 THE EFFECT OF NANO SiO2 in CMC – and DUOVIS DFs ... 95
7.3 THE EFFECT OF NANO SiO2 in EOR... 97
7.4 DISCUSSION OF THE SIMULATION RESULTS ... 99
8 CONCLUSION ... 100
APPENDIX ... 102
APPNEDIX A: AMPLITUDE SWEEP TEST RESULTS ... 102
APPENDIX B: SETUP FOR WELLPLAN AND WELLPATH ... 106
APPENDIX C: CORE FLOODING ... 108
APPENDIX D: CORRECTION FACTOR FOR TENSIOMETER ... 111
APPENDIX E: FANN VISCOMETER RESULTS ... 112
APPENDIX F: PHOTOS OF CORE FLOODING EXPERIMENTAL SETUP... 113
REFERENCES ... 116
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LIST OF FIGURES
FIGURE 1 A GRAPHICAL OVERVIEW OF THE DISTRIBUTION OF OIL FIELDS AND RESOURCES ON NCS PER 31.12.2017.[1] ... 13
FIGURE 2 METHOD OF RESEARCH ... 16
FIGURE 3 LOGARITHMIC SCALE OF SIZES OF LIVING THINGS [14] ... 17
FIGURE 4 AN ILLUSTRATION OF SHEAR STRESS – SHEAR RATE TRENDS FOR DIFFERENT FLUID TYPES [26] ... 24
FIGURE 5 STRESS – STRAIN REACTION FOR AN OSCILLATORY COMPUTATION OF A VISCOELASTIC MATERIAL [29] ... 30
FIGURE 6 GRAPHICALLY SHOWING PARAMETERS SUCH AS GEL – CHARACTER ON THE LEFT-HAND SIDE, WHILE YIELD POINT AND FLOW POINT IS PRESENTED ON THE RIGHT-HAND SIDE [27] ... 33
FIGURE 7 A SEGMENTED STRING AND THE ASSOCIATED LOADS [26] ... 34
FIGURE 8 COMMON CURVES FOR RELATIVELY PERMEABILITY FOR DRAINAGE – AND IMBIBITION PROCESS AT WATER WET SYSTEMS [30] ... 39
FIGURE 9 INTERFACIAL TENSIONS FOR OIL – WATER – SOLID SYSTEM AT EQUILIBRIUM [30]. ... 40
FIGURE 10 TYPICAL CAPILLARY PRESSURE VERSUS SATURATION RELATIONSHIP [30]. ... 42
FIGURE 11 TYPICAL CLAY STRUCTURE [13] ... 45
FIGURE 12 THE DIFFERENT CLAY CONDITIONS [12]. ... 46
FIGURE 13 THE MOLECULAR STRUCTURE OF CARBOXYMETHYL CELLULOSE [39] ... 48
FIGURE 14 THE SALT COMPONENTS OF SEAWATER [42] ... 50
FIGURE 15 SCANNING ELECTRON MICROSCOPY (SEM) IMAGE OF COMMERCIAL SIO2 ... 52
FIGURE 16 THE ELEMENT ANALYSIS OF SIO2 OBTAINED BY ENERGY DISPERSIVE SPECTROGRAPH. ... 52
FIGURE 17 THE MECHANISM BEHIND ALTERATION OF WETTABILITY [44] ... 54
FIGURE 18 THE MECHANISM BEHIND DISJOINING PRESSURE [44] ... 55
FIGURE 19LEFT:MAGNETIC STIRRER RIGHT:ULTRASONICATOR ... 57
FIGURE 20 VISUAL APPEARANCE OF THE FORMULATED NANOFLUIDS WITH DIVERSE CONCENTRATIONS ... 57
FIGURE 21TENSIOMETER FOR DU NOÜY RING METHOD ... 59
FIGURE 22 THE SURFACE TENSION FOR WATER IN DIFFERENT TEMPERATURES ... 60
FIGURE 23:A GRAPHICALLY PRESENTATION OF THE IFT VALUES OBTAINED FOR THE DIFFERENT FLUID SYSTEMS ... 62
FIGURE 24 A GRAPHICALLY PRESENTATION OF THE CONTACT ANGLES FOR VARIED FLUID SYSTEMS. ... 63
FIGURE 25THE CONTACT ANGLE MEASURED BY KRÜSS DROP SHAPE ANALYSIS SYSTEM... 64
FIGURE 26 A HOOKED NEEDLE OF THE SYRINGE, AND THE GLASS CONTAINER SETUP FOR THE CA MEASUREMENTS WITH THE DROP SHAPE ANALYSER ... 64
FIGURE 27 A SCHEMATIC FIGURE OF THE CORE FLOODING SETUP AT IRIS ... 65
FIGURE 28 THE ULTIMATE RECOVERY FACTOR FOR CORE 3 WITH THE FUNCTION OF CUMULATIVE INJECTED PV ... 69
FIGURE 29 A PLOT OF THE MEASURED VALUES OBTAINED BY FANN VISCOMETER FOR CMC BASED SYSTEMS ... 72
FIGURE 30 CALCULATED PARAMETERS SUCH AS PV,YS AND LSYS IN REGARD OF BINGHAM MODEL FOR CMC BASED DRILLING FLUIDS. ... 72
FIGURE 31 COEFFICIENT OF FRICTION FOR THE VARIOUS CMC BASED DRILLING FLUID SYSTEMS OBTAINED BY TRIBOMETER. ... 74
FIGURE 32 A PLOT OF THE MEASURED VALUES OBTAINED BY FANN VISCOMETER FOR DUOVIS BASED SYSTEMS ... 76
FIGURE 33 CALCULATED PARAMETERS SUCH AS PV,YS AND LSYS IN REGARD OF BINGHAM MODEL FOR DUOVIS BASED DRILLING FLUIDS. ... 76
FIGURE 34 COEFFICIENT OF FRICTION FOR THE VARIOUS DUOVIS BASED DRILLING FLUID SYSTEMS OBTAINED BY TRIBOMETER. ... 78
FIGURE 35 A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF DUOVIS ... 79
FIGURE 36 SHEAR STRESS VALUE AT THE FLOW POINT FOR THE CMC– AND DUOVIS BASED DIFFERENT DRILLING FLUID SYSTEMS .... 81
FIGURE 37 THE DIFFERENT RHEOLOGICAL MODELS FOR REF CMC DRILLING FLUID SYSTEM ... 83
FIGURE 38 THE DIFFERENT RHEOLOGICAL MODELS FOR CMC+0.025SIO2 DRILLING FLUID SYSTEM ... 84
FIGURE 39 THE DIFFERENT RHEOLOGICAL MODELS FOR REF DUOVIS DRILLING FLUID SYSTEM ... 85
FIGURE 40 THE DIFFERENT RHEOLOGICAL MODELS FOR REF DUOVIS +0.050G SIO2 DRILLING FLUID SYSTEM ... 86
FIGURE 41COMPARING THE PERFORMANCE OF THE DUOVIS DFS FOR TOTAL PRESSURE LOSS ... 89
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FIGURE 42 COMPARING THE PERFORMANCE OF THE DUOVIS DF FOR ECD ... 89
FIGURE 43 COMPARING THE PERFORMANCE OF THE CMCDFS FOR TOTAL PRESSURE LOSS ... 90
FIGURE 44 COMPARING THE PERFORMANCE OF THE CMCDFS FOR ECD ... 90
FIGURE 45THE SETUP FOR SIMULATION OF TORQUE AND DRAG ON WELL PLAN ... 91
FIGURE 46COMPARING THE PERFORMANCE OF CMCDFS IN TERMS OF TORQUE LIMIT ... 92
FIGURE 47 COMPARING THE PERFORMANCE OF CMCDFS IN TERMS OF TENSILE LIMIT ... 93
FIGURE 48A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF CMC ... 102
FIGURE 49A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF CMC+0.025SIO2 ... 102
FIGURE 50A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF CMC+0.050SIO2 ... 103
FIGURE 51A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF CMC+0.075SIO2 ... 103
FIGURE 52A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF DUOVIS ... 104
FIGURE 53A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF DUOVIS +0.025SIO2 ... 104
FIGURE 54A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF DUOVIS +0.050SIO2 ... 105
FIGURE 55A DIAGRAM OF AMPLITUDE SWEEP MEASUREMENTS FOR REF DUOVIS +0.075SIO2 ... 105
FIGURE 56PRE SET PARAMETERS FOR THE SIMULATION SETUP ... 106
FIGURE 57A GRAPHICAL ILLUSTRATION OF THE WELL AND DRILL STRING ... 106
FIGURE 58INCLINATION VERSUS MEASURED DEPTH ... 107
FIGURE 59AZIMUTH VERSUS MEASURED DEPTH ... 107
FIGURE 60RECOVERY FACTOR DURING PRE WATER FLOODING FOR CORE 1 ... 108
FIGURE 61RECOVERY FACTOR DURING INJECTION OF NF FOR CORE 1 ... 108
FIGURE 62RECOVERY FACTOR DURING POST WATER FLOODING FOR CORE 1 ... 109
FIGURE 63RECOVERY FACTOR DURING PRE WATER FLOODING FOR CORE 3 ... 109
FIGURE 64RECOVERY FACTOR DURING INJECTION OF NF FOR CORE 3 ... 110
FIGURE 65RECOVERY FACTOR DURING POST WATER FLOODING FOR CORE 3 ... 110
FIGURE 66EQUATIONS FOR CORRECTION FACTOR AND THE REQUIRED PARAMETERS ... 111
FIGURE 67THREE BEREA SANDSTONE CORE PLUGS ... 113
FIGURE 68A CORE WITHIN THE CORRESPONDING CORE - SLEEVE ... 113
FIGURE 69AVACUUM PUMP ... 114
FIGURE 70A CAMERA TO KEEP RECORDS OF ANY OIL PRODUCTION... 114
FIGURE 71THE SETUP FOR CORE FLOODING AT IRIS ... 115
FIGURE 72THE CORE HOLDER WITH THE CORE INSIDE OF IT ... 115
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LIST OF TABLES
TABLE 1SUMMARY OF ALL APPLICATIONS OF NANOTECHNOLOGY ... 18
TABLE 2RESULTS OF FLOODING TESTS OBTAINED BY JAFARI ET AL.(2015)[18] ... 20
TABLE 3MIXTURE CONCENTRATION RATIOS USED FOR FLOODING [19] ... 21
TABLE 4THE GIVEN CATEGORIES OF VISCOELASTIC MATERIAL OBTAINED BY AN OSCILLATORY MEASUREMENT [27] ... 31
TABLE 5A SUMMARY OF EQUATIONS ASSOCIATED WITH THE UNIFIED RHEOLOGICAL MODEL [25] ... 36
TABLE 6WETTABILITY PREFERENCES GIVEN BY THE CONTACT ANGLE [32] ... 41
TABLE 7THE COMPONENTS OF BENTONITE [35] ... 44
TABLE 8THE FORMULA FOR THE DESIGNED NANOFLUID SYSTEM WITH VARY CONCENTRATIONS OF SIO2 ... 56
TABLE 9THE MEASURED VISCOSITY AND DENSITY VALUES FOR THE ASSOCIATED NANOFLUID SYSTEMS. ... 58
TABLE 10MEASURING THE PERMEABILITY BEFORE AND AFTER INJECTION OF NANOFLUID FOR THE VARIOUS CORES. ... 67
TABLE 11FORMULATION OF THE DESIGNED CMC BASED DRILLING FLUID SYSTEMS ... 70
TABLE 12THE FORMULATION OF THE DUOVIS BASED DRILLING FLUID SYSTEMS ... 75
TABLE 13THE EQUATION AND PARAMETERS FOR THE DIFFERENT RHEOLOGICAL MODELS REGARDING REF CMC ... 82
TABLE 14THE EQUATION AND PARAMETERS FOR THE DIFFERENT RHEOLOGICAL MODELS REGARDING CMC+0.025G SIO2 ... 83
TABLE 15THE EQUATION AND PARAMETERS FOR THE DIFFERENT RHEOLOGICAL MODELS REGARDING REF DUOVIS ... 84
TABLE 16THE EQUATION AND PARAMETERS FOR THE DIFFERENT RHEOLOGICAL MODELS REGARDING DUOVIS +0.050G SIO2 ... 85
TABLE 17A SUMMARY OF RHEOLOGICAL MODELS WITH THE PARAMETERS AND DEVIATIONS IN TERMS FOR THE VARIOUS DRILLING FLUID SYSTEMS. ... 87
TABLE 18A SUMMARY TABLE OF PROLONGED MEASURED DEPTH OF DRILLING FOR THE SELECTED DRILLING FLUID SYSTEMS. ... 93
TABLE 19SUMMARY OF THE INFLUENCE OF NANO SIO2IN REGARDS OF IFT AND CA. ... 98
TABLE 20A SUMMARY OF THE MEASURED IFT VALUES, AND THE CORRESPONDING CORRECTED IFT ... 111
TABLE 21DATA OF VISCOMETER FOR DUOVIS BASED DFS ... 112
TABLE 22DATA OF VISCOMETER FOR CMC BASED DFS ... 112
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NOMENCLATURE
OBM Oil Based Mud
WBM Water Based Mud
DF Drilling Fluid
NF Nano Fluid
SBM Synthetic Based Mud
NS Nano Solution
WF Water Flooding
PF Polymer Flooding
NPF Nano Polymer Flooding
PV Plastic Viscosity, Pore Volume
LVER Linear Viscoelastic Range
ECD Equivalent Circulating Density
CMC Carboxymethyl Cellulose
KCl Potassium Chloride
SEM Scanning Electron Microscope
EDS Energy Dispersive Spectrograph
EOR Enhanced Oil Recovery
IFT Interfacial Tension
CA Contact Angle
SW Seawater
YS Yield Stress
LSYS Lower Shear Yield Stress
BF Base Fluid
REF Reference
HB Herschel Bulkley
RS Robertson and Stiff
NP Nanoparticle
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1. INTRODUCTION
The presentation of the thesis will at the majority of the time focuses on the effect of SiO2
nanoparticles as implemented in drilling fluids and enhanced oil recovery techniques. In the course of the thesis, a stabilized SiO2 nanofluid have been designed and characterized. The evaluation of the influence in terms of raising the oil recovery was highlighted with core flooding of Berea sandstones, reducing interfacial tension and changing the wettability.
Further, the impact of nanoparticles was studied in drilling fluids as the objective is to achieve desired performance to improve the functions of drilling fluids.
1.1. BACKGROUND & MOTIVATION
There is no secret that the world’s population has increased rapidly in the recent decades, and our modern lifestyles have altered the necessity of more energy. The demand for energy has been increased simultaneously with the years, and even though our scientists have been seeking for other options for energy, the oil and gas industry remains as the number one provider of energy. To be able to keep providing the demanding energy, the industry must seek for another solution than the current way of producing fossil fuel beneath the surface.
Higher risks have been taken in form of expanding the exploration for the hydrocarbons, further challenges have been encountered as drilling wells have been found in environments with higher temperature and pressure, as well as the challenges due to drilling in the arctic.
[1] [2]
Nanotechnology has been an exciting term within the modern technology and has highly potential to alter the current technology. In fact, industries as medicine, electronics and food science have already proved nanotechnology’s worth in their respectively operations. [3]
Although numerous of positive impressions from precedingly researched reports, the fate for the Nano-sized materials have not been decided yet in the oil and gas industry, and the protentional application of nanotechnology in current methods have currently been left out.
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The following subsections will briefly introduce the basic principle of conventional technology within enhanced oil recovery and drilling fluids, as well as the drawbacks.
1.1.1. ENHANCED OIL RECOVERY
As one of four major processes of oil and gas industry, the production process may be categorized into three main stages:
1. Primary recovery 2. Secondary recovery 3. Tertiary recovery (EOR)
In the first development of the production process, the major mechanism of oil recovery is namely the pressure differential. Higher pressure in the reservoir than in the recent drilled wellbore will make the hydrocarbons stream into the well and up to the surface. The combination of the pressure differential, pumps and the assistance of lift techniques is the characterization of the primary recovery stage. [4]
In the next stage of the recovery process, the objective is to maintain the reservoir pressure to keep it from reaching the bubble point pressure and avoid further gas production.
To be able to achieve the maintenance of the reservoir pressure, secondary recovery has to be made, and it consist of injection of either water or gas to displace the oil. During the secondary recovery, the oil recovery of the original oil in place can be predicted to be between 20 – 40%. [5] [6]
The final stage of the production process is called for tertiary recovery, but rather known as enhanced oil recovery due to all application of any further method to increase the recovery percentage from the reservoirs which alters from the primary and secondary recovery.
At the moment, there exists three leading enhanced oil recovery techniques which should increase the ultimately oil recovery further to 30 – 60%: [6]
1. Thermal recovery 2. Gas injection 3. Chemical injection
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The diagram below presents an overview of the distribution of oil fields and resources on the Norwegian Continental Shelf graphically. As it shows both produced and remaining oil reserves, a report achieved by the NPD states the current recovery factor to be an average on 47%. In fact, the report implies that even higher recovery factor can be achieved. [7]
Figure 1 A graphical overview of the distribution of oil fields and resources on NCS per 31.12.2017. [1]
1.1.2. DRILLING FLUID
The drilling fluid plays a crucial part of any drilling operation. Among many functions, drilling fluids are mainly used to transport cuttings to surface and maintain well pressure. Besides the mentioned functions, cooling, cleaning and lubricating the drill bit are also importance to avoid damaging the bit. [8]
The ordinary types of drilling fluid can be classified into fluid systems such as oil-based mud (OBM), water-based mud (WBM) and synthetic based mud (SBM). The right pick of drilling fluids relies on handful factors such as technical performance, cost and environmental impacts. [9]
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If drilling fluids are formulated below par, the consequences may lead to drilling related problems such as formation damage, mud loss, drill string sticking, clay swelling, high torque and drag and insufficient hole cleaning and hydraulic performances. [10] [11]
According to reports, 75% of drilling formations consist of shale where the occurrence of well instability has been recorded to be a major issue. Usually, oil-based drilling fluid is better than water-based drilling fluid regarding swelling control of shales, and additional due to higher lubricity result in better torque-drag performance. However, it is expensive and environment unfriendly compared to water-based mud. [11]
Consequently, to avoid the drilling issues which occurs due to drilling of shale formations, the development of water-based mud with the equal performance of oil-based mud is decisive for the future drilling operations, as well as to be more concern about the environmental aspect.
[12] [13]
1.2. FORMULATION OF THE PROBLEM
It has been previously shown that conventional technologies regarding EOR and drilling fluids have shortcomings. Successful solutions have been documented in the literature in terms of utilizing the nanotechnology in oil and gas industry. However, both the research and development are still at an early stage.
This thesis will therefore address issues such as:
• How nanofluid of SiO2 in brine systems can have an impact on oil/rock surface energy to improve oil recovery?
• How nanoparticles of SiO2 can have an impact on drilling fluid properties?
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1.3. OBJECTIVE
The foremost objectives of this thesis are to formulate SiO2 Nano-fluid, characterize, and as well to test the performances of the nanofluids in drilling fluid and EOR.
The activities are:
• Review applications of nanotechnology in EOR and drilling fluids
• Experimental investigation
• Simulation of the performance
1.4. METHOD OF RESEARCH
The methods of research for the thesis can be categorized into three major parts. The figure 2 presents these parts, as well as the highlighted sections for their respectively major parts.
The first major part introduces the extensive literature study for the relevant theories utilized in the work of this thesis, information for the chemical additives and the applications of nanoparticles in terms of EOR.
The second part deals with the experimental work of the influence nanoparticles in EOR and drilling fluids, where the formulation, characterization and tests will be found.
While, the last part presents the simulation of the modelling for the drilling fluids.
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Figure 2 Method of Research MSc Thesis work
Literature study
Theory
Application of nanoparticles Chemical
ingredients used for the thesis
Experimental
Rheology
Tribology
Viscoelasticity
Core floowing
IFT
Contact angle
Simulation
Rheological modelling
Hydraulics
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2. LITERATURE STUDY
Nanotechnology as a term, as well as a few applications of nanotechnology in the oil and gas industry will be presented in the following sections.
2.1. NANOTECHNOLOGY
The term nanotechnology is primary engineering of functional systems at the scale of molecular. Strictly speaking, the definition of nanotechnology can be smoother described as the science, technology and engineering to manipulate at a nanoscale. The range of a nanoscale is approximately within 1 – 100 nanometres.
Unlike most things, the range of nanoscale does not relate to us humans, as it may be difficult to imagine as well. A nanometer is in fact a billionth of a meter, and in a more mathematically way is equivalent to 10-9 of a meter.
The following figure 3 will give the idea of how tiny the scale is related with other objects.
Figure 3 Logarithmic scale of sizes of living things [14]
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The greatest remarked advantage by applying nanoparticles rather than materials at macroscale, is the high ratio of surface to volume. In other words, this implies that particles within the nanoscale could be applied at a sufficient lower concentration and still have greater interactions due to the greater area. Successfully applications of nanotechnology can already be found in such as medicine – and electronic industry. [15] [3]
2.2. APPLICATIONS OF NANOTECHNOLOGY
The major investigation of the thesis work is highlighted in this section as the potential applications of nanotechnology are under scope. As mentioned earlier, nanotechnology have been adapted in several other sectors such as electronics, pharmaceutical and food science.
The extensive study focuses mainly on enhancing the oil recovery.
Reference NPs / Basefluid Oil type Rock type % Additional
Ultimate Oil Recovery
Effect factor
Elgibaly SiO2 / Brine Black oil Sandstone 12,7 % NP
concentration
Kharrat SiO2 / Brine Heavy crude
oil
Glass 26 % Wettability
concentration
Jafari SiO2 / Polymer N/A Glass
micromodel
18,37 % Wettability
Sweep efficiency Tarek Al2O3 + Fe2O3 +
SiO2
Mineral oil Sandstone 20 % Concentration
Sweep efficiency (Fe2O3)
Ehtesabi TiO2 N/A Carbonate 31 % Wettability
Concentration
Torsæter SiO2 / Brine Light Crude oil Berea SS 12 % IFT
Contact angle Concentration
Roustei SiO2 / Brine N/A Carbonate 25 % Wettability
Wang SiO2 / Brine N – Decane Calcite - Wettability
concentration Table 1 Summary of all applications of Nanotechnology
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Elgibaly et al. (2017) presents the influence of commercial hydrophilic mono dispersed silica (SiO2) nanoparticles in enhanced oil recovery. The nanoparticles were 20 nm in size, and where tested in different aspects to affect oil recovery as a whole.
The authors of the papers acknowledge that nanoparticles have several mechanisms to improve oil recovery such as disjoining pressure mechanism and wettability alteration mechanism which is addressed in Section 4.7.
The experimental work conducted by Elgibaly et al. (2017) compared the efficiency of adapting Nano silica in either secondary – or tertiary recovery technique, as well as investigating the optimum concentration of nanoparticles. The oil recovery percentage increases simultaneously with increasing concentration of silica nanoparticles up to 0.1 wt% which was found as the optimum concentration and gave an additional 12,7% oil recovery. [16]
Due to minimal difference in secondary and tertiary recovery by using SiO2, waterflooding may still be the best option to secondary recovery since it is the most reliable and economic compared to Nano silica.
Additionally, the authors address permeability impairment is an issue, and in this paper, both injection rate of the nanofluid and the concentration of the fluid show to have a direct effect of permeability impairment.
While, Ogolo et al. (2012) compares the impact of nine diverse oxide nanoparticles such as Aluminium oxide, Nickel oxide, Magnesium oxide, Iron oxide, Zinc oxide, Zirconium oxide, Tin oxide, Silicon oxide treated with silane and hydrophobic Silicone oxide. In order to evaluate the beneficence of applying nanoparticles for the total oil recovery, the various oxide nanoparticles were tested with different dispersing agents (distilled water, ethanol, brine and diesel). [17]
The methods of core flooding were set into either to apply nanofluids to flush a pre-injected pack of sand with brine and oil, or was to additionally soak the preinjected pack of sand with nanofluids for 60 days which gave the least best result among these methods.
The authors made two quite important observations:
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Firstly, distilled water gave poorly recover overall, even with nanoparticles involved.
Secondly, often the presence of nanoparticles with ethanol or brine did not enhance the oil recovery if compared to same respectively fluids without nanoparticles.
Overall, according to the authors, Aluminium oxide in brine and Silicone oxide in ethanol were both promising candidates for enhancing the oil recovery. While ethanol may be used singly to improve the total oil recovery.
Nano silica is popular as the nanoparticles have shown to be a great potential EOR agent, and Jafari et al. (2015) have included a polymer in a solution containing Nano silica. To be able to fully reveal the influence of the nanoparticle on wettability alternation of the porous medium, three flooding tests including water flooding (WF), polymer flooding (PF) and Nano – polymer flooding (NPF) were conducted. [18]
As shown in the following table 2, both the polymer and NS improves the oil recovery about 10% and 20%, respectively, compared to water itself.
The reason is the higher viscosity of the injected fluid that improves the oil displacement, and additionally it is obtained that NS can alter the wettability of the medium from oil – wet condition to water – wet. For this reason, Nano silica has the ability to lower the thickness of oil layer which allows the polymer to adsorb on pore walls and higher sweep efficiency has been achieved.
Test Breakthrough time [min]
Ultimate recovery [%]
Viscosity of the injected fluid [cP]
WF 42 16.63 1
PF 64 26.32 8
NPF 84 35.00 35
Table 2 Results of flooding tests obtained by Jafari et al. (2015) [18]
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The performance of a potential mixture of several nanoparticles to enhance the oil recovery rather than solely one nanoparticle was studied thoroughly by Tarek et al. (2015) from Cairo University. [19]
The author chose to base the alternatives of nanoparticles by two main criteria:
• The increased amount of oil recovery
• The mechanism of the nanoparticle which is responsible for the enhanced oil recovery Former papers suggest both Aluminium Oxide and Iron Oxide as good candidates for the mixture of nanofluid due to their significant oil recovery ability.
Silica Oxide is another candidate to join the mixture of this investigation due to be proven to alter the wettability to water wet formation. Oil wet formation is by far poorer than water wet formation in regards of production, and additionally, SiO2 forms a wedge – layer between the surface of the rock and the particular oil droplet. [19]
In this investigation, core flooding was the major part of the experimental work and the ratios of different nanoparticles are shown in the following table 3.
Mixture Al2O3 Fe2O3 SiO2
1 40 % 20 % 40 %
2 33.33 % 33.33 % 33.33 %
3 35 % 40 % 25 %
Table 3 Mixture concentration ratios used for flooding [19]
The results showed the mixture 3 gave the most promising result as it gave 20% additional incremental oil recovery due to the higher concentration of Iron Oxide which dominates the effect of granting higher viscosity to enhance the sweep efficiency. Mohamed Tarek concludes in the end that a mixture of nanoparticles may be a better option for recovery than a singular nanoparticle, and the importance of the ratio of the nanoparticle within the mixture.
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On the other hand, Ehtesabi et al. (2013) studied the influence of Titanium Oxide to enhance heavy oil recovery on sandstone cores. The paper explains thoroughly all the aspect of the application of Titanium Oxide, from synthesis of nanofluid, its stability, testing the influence for oil recovery and as well the mechanisms behind it. [20]
A regular waterflooding was first conducted to set the baseline, and the performance of water itself was approximately 49% as recovery factor. By injecting with Titanium Oxide 0.01% gave a significant jump of recovery factor up to 80%, while injecting 1% nanoparticles had the opposite effect as the value was even lower than without TiO2.
The higher recovery factor by injecting TiO2 can be explained by altering the wettability due to increasing the contact angle of oil droplets after the injection. During the characterization, the SEM image of the core revealed higher accumulation of nanoparticles in the entrance rather throughout the core itself shows the importance to study the deposition and concentration of these nanoparticles.
The possibility of applying hydrophilic Silica to an enhanced oil recovery method was investigated by Torsæter et al. (2013), as well as to find the major mechanisms behind these nanoparticles by conducting experiments as transparent glass micromodel for two – phase flooding experiment and core flooding with Berea sandstones. [21]
The interfacial tension has been mentioned to be a key factor as a mechanism for Silica nanoparticles for EOR purposes, while the contact angle is another measurement that can describe the wettability. Measurements were conducted in this paper by utilizing a SVT20 spinning drop and Goniometry KSV Cam instrument, respectively. The conclusions are such as:
• Hydrophilic Silica nanoparticles dispensed with synthetic brine have the ability to reduce the interfacial tension between water – and oil phase.
• Higher concentrations of nanoparticles result with lower interfacial tension
• 0.05 wt % of Silica nanoparticle was found to be the optimum concentration in regard of oil recovery as the value increased by 12%
• Silica nanoparticles can reduce the contact angle
Half of the known petroleum reserves in the whole world is in fact in carbonate rocks, and among these, 90% of them can be labelled as neutral to oil – wet. The wettability is an
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important property to be able to understand how the fluid flows in the reservoirs, and since there are difficulties to recovery sufficient oil of carbonate reservoirs by conducting the standard waterflooding, Roustei et al. (2014) introduces Silica nanoparticles as a candidate to improve the oil recovery.
In this investigation, the experimental work has been divided into core flooding, and test of contact angles and interfacial tension. [22].The authors of this paper concluded following points:
• Silica nanoparticles can be considered as a good candidate to alter the wettability for carbonates from oil – wet to water – wet.
• Overall oil recovery hits 67%
Kharrat et al. (2012) performed core flooding test of silica nanoparticles displacing heavy oil.
A five – spot glass micromodel was utilized as the porous media, while both dispersed nanoparticles of silica in water and distilled water were chosen to be injected.
During the core flooding, an optimum concentration of nanoparticle was found to be at 3 wt.%
among the chosen range of concentration. The solution with 3 wt.% gave an additional 26%
ultimate oil recovery compared to waterflooding. The investigation also presents the mechanism behind the success of enhancing the oil recovery by revealing the great sweep efficiency as the whole reason and labelled by having higher percentage of Nano silica in the water. Lastly, a suggestion by the authors is to utilize Nano silica as an additive to the solution during waterflooding before applying any other EOR techniques. [23]
Another investigation of Nano silica is reviewed by Wang et al. (2015) as their objective is mainly focusing on the study of contact angle and wettability.
Nanofluids containing silica proves to alter the wettability of calcite surfaces from oil – wet to strongly water – wet which is a superior condition in terms of oil recovery. The lowest amount of nanoparticle concentration to be sufficient to be able to make a difference for the contact angle was found to be 1 – 2 wt.%. Additionally, the exposure time of nanofluids on the calcite surfaces is also to be considered.
Overall, Nano silica can be a great additive to the solution to enhance the alteration of wettability as the EOR mechanism to produce more oil. [24]
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3. THEORY
The third chapter of the thesis will present the relevant theories for the further work in the experimental study, as well as the simulation part for the performance of the drilling fluids.
3.1 RHEOLOGY
In order to be able to describe any fluids, numerous diverse mathematical models have been occurred. These models offer correction for the unique type of fluid. Fluids in general can be described as either Newtonian, Plastic, Pseudo plastic or dilatant fluids. The correct rheological model has to be applied to the right fluid category as these models will determine parameters such as gel strength and the viscosity of the fluid. These properties express the behaviour of the fluid, as well the ability to suspend and transport the cuttings from the wellbore to the surface. The figure 4 shows the relation between the shear stress and shear rate for the various types of fluids. [12] [25]
Figure 4 An illustration of shear stress – shear rate trends for different fluid types [26]
25 Plastic Viscosity: (𝑃𝑉)
The plastic viscosity term describes the resistance to flow caused by the mechanical friction found either between the particles suspended in the fluid, between the particle and the fluid, or among the fluid elements. Parameters such as the viscosity of the fluid, the size and shape of the additives in the fluid and the concentration of the additives influences the plastic viscosity. The determination of the plastic viscosity can readily be calculated by the following equation:
𝑃𝑉 = 𝜃600− 𝜃300 1
Where the 𝜃600 and 𝜃300 are the reading of a viscometer at 600 RPM and 300 RPM shear rate, respectively. [12]
Yield Stress (YS):
While PV describes the resistance to flow caused by mechanical friction, the yield stress occurs because of attractive forces caused by the electrostatic forces among the particles in the fluid.
The yield stress value will be heavily dependent of the shear rate, and reduces as the shear rate increases. In that case, the fluid is a shear – thinning fluid if it fulfils the mentioned character. [12]
𝑌𝑆 = 2𝜃300− 𝜃600 2
Gel Strength:
If a fluid is thick or even viscous under a static condition, but alters to a thinner fluid after shear strain is applied, the fluid will be categorized to have thixotropic behaviour. In other means, the shear stress is not constant for a certain rate, but rather alters as a function of shear rate. The gel strength describes the attractive forces between the suspended particles in a static fluid, and measures as a function of time. [12]
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3.2 RHEOLOGICAL MODELS
In general, all fluids can either be classified in Newtonian – and Non – Newtonian fluids. These terms will be briefly described in the following subsections, and some rheological models will moreover be presented.
3.2.1 NEWTONIAN FLUIDS
The characterization of a Newtonian fluid is the independence of shear rate for the viscosity.
For instance, the behaviour of a Newtonian fluid can be found in either water, oil or glycol due to containing no greater particles than molecules.
Due to that shear stress is directly proportional to shear rate, the relation between them graphically forms a straight line from the origin in the diagram. [12]
The following equation describes all Newtonian fluids:
𝜏 = 𝜇 ∙ 𝛾 3
Where 𝜏 is the shear stress, 𝜇 is the viscosity of the fluid and 𝛾 is the shear rate.
3.2.2 NON – NEWTONIAN FLUIDS
While most fluids do not tend to be classified to be a Newtonian fluid, the viscosity of non – Newtonian fluids relies on the shear rate. By its nature, drilling fluids can be described as non – Newtonian fluids and several models have been developed and presented in the following subsections: [12]
BINGHAM PLASTIC MODEL
The Bingham plastic model is characterized by three parameters, while the shear stress and strain are linearly related [12]. The rheological model presumes that the drilling fluid has a constant viscosity for all shear rates, as well as having a higher yield stress at very low shear
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rates. However, these two properties are not observed in drilling fluid. The definition of Bingham plastic model is expressed as follows [25]:
𝜏 = 𝜇𝑝𝛾 + 𝜏𝑦 4
Where, p and y are the plastic and yield strength of the drilling fluid, respectively.
POWER LAW MODEL
Regarding of the shear thinning beavhiour of drilling fluids, the Power Law model is more fitted to describe the fluid than the Bingham plastic model. Although, the Power Law model does not characterize the fluids at very low shear rate. The model is a two-parameter model, while the definition is given by the expression [12]:
τ = Kγn 5
where the consistence index and the flow behaviour index are symbolized with K and n, respectively, and can be calculated from the data obtained by the viscometer as:
𝑛 = 3.32log (𝑅600
𝑅300) 6
𝐾 = 𝑅300
511𝑛 = 𝑅600
1022𝑛 7
HERSCHEL – BULKLEY MODEL
The Herschel-Bulkley model is a yielded power law model and is better fitted to characterize the rheological properties of drilling fluid than both the Power Law – and Bingham Plastic model. The equation for the Herschel – Bulkley model is given as [12]:
𝜏 = 𝜏0+ 𝐾𝛾𝑛 8
Where the τ and τ0 is shear – and yield stress, and γ is the shear rate, and the latter symbols have been described in the Power Law model.
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τ0 = τ∗2− τminτmax
2τ∗− τmin− τmax 9
While the parameter τ* is obtained by interpolation of the equivalent shear rate, γ* value, which is given as:
𝛾∗ = √𝛾𝑚𝑖𝑛− 𝛾𝑚𝑎𝑥 10
UNIFIED MODEL
This model is a customized form of the Herschel-Bulkley model including to simplify it. The difference is the reduced shear yield point, and the equation is given as [12]:
𝜏 = 𝜏𝑦+ 𝐾𝛾𝑛 where the 𝜏𝑦 = 1.066 (2𝑄3− 𝑄6) 11
ROBERTSON AND STIFF MODEL
This rheological model has proven to be better in comparison to both Bingham – and Power Law model, but is far from the most popular due to the complexity as the equation shows [12]:
τ = A(γ + C)B 12
Where both A and B is the equivalent parameters such as K and n for the other rheological models, while C is the correction factor to the shear rate.
C = γmaxγmin− γ∗2
2γ∗− γmax− γmin 13
Where γ* is the shear rate value which is determined by interpolation from the shear stress, τ*:
τ ∗= √τmin∗ τmax 14
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3.3 VISCOELASTICITY
The behaviour of viscoelasticity can be presented by the materials composed of both solids and fluids. For instance, a drilling fluid exhibit the nature of a viscoelastic substance. This means a drilling fluid can be both characterized in regards of elasticity and of viscosity under deformation due to having suspended particles in an aqueous solution.
The properties of a viscoelastic material rely upon time. The alteration of either shear stress or shear rate can influence the viscosity, either increasing it or decreasing it.
In a combination of applying higher shear stress to the subject, and time, the viscosity increases. Although, like most, an ideal amount of applied shear stress can be found, since higher shear stress causes heating as well. Higher temperatures will in fact reduce the value of viscosity. [27]
During applying deformation to the drilling fluid, the property of elasticity can store energy which influences the pressure drop and how the fluid flows. Hence, the vital knowledge of viscoelasticity as describes properties such as solid suspension, gel structure and gel strength, and hydraulic sagging. In order to define the viscoelasticity to a drilling fluid mixture, a rheometer can conduct test such as oscillatory test to evaluate and describe the importance of viscoelasticity. [28]
The rheometer has the ability to define the viscoelasticity by using a simple basis rule of the Two – Plates model of an oscillatory test. The sample of the chosen subject is firstly carefully placed upon the cleaned lower plate which is stationary, while the upper plate will press the sample between the two plates. Additionally, the upper plate will also perform shear stress upon the sample as the upper plate moves in oscillatory way throughout the test.
By the time the rheometer is running the test, the selected sample between the plates will experience different sinusoidal deformation, strain. As the deformations takes place, the stress will be measured and plotted into the program. The following figure 5 shows how the behaviour of both strain and stress is during the test as a function of amplitude, time and phase angle.
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Figure 5 Stress – strain reaction for an oscillatory computation of a viscoelastic material [29]
The following definitions are the computational shear stress, and the shear strain applied to
the selected sample [28]:
𝜏(𝑡) = 𝜏𝑜[sin(𝜔𝑡) 𝑐𝑜𝑠𝛿 + cos(𝜔𝑡) 𝑠𝑖𝑛𝛿] 17 𝜏(𝑡) = 𝛾0[(𝜏𝑜
𝛾0𝑐𝑜𝑠𝛿) sin(𝜔𝑡) + (𝜏𝑜
𝛾0𝑠𝑖𝑛𝛿) cos(𝜔𝑡)] 18 𝜏(𝑡) = 𝛾0[𝐺′sin(𝜔𝑡) + 𝐺′′cos(𝜔𝑡)] 19
These equations are defined for the Storage – and the Loss Modulus, respectively [28]:
𝐺′= (𝜏𝑜
𝛾0𝑐𝑜𝑠𝛿) 20
𝐺′′ = (𝜏𝑜
𝛾0𝑠𝑖𝑛𝛿) 21
𝜏(𝑡) = 𝜏𝑜sin(𝜔𝑡 + 𝛿) 15
𝛾(𝑡) = 𝛾𝑜sin(𝜔𝑡) 16
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While, the damping factor is defined as the ratio of the Loss - and the Storage Modulus:
𝑡𝑎𝑛𝛿 = (𝐺′′
𝐺′) 22
𝛿 = 𝑡𝑎𝑛−1(𝐺′′
𝐺′) 23
As described for the damping factor equation, the symbol, δ, defines the parameter which alters regarding to the fluid and is known as the phase angle.
The table 4, represents the different scenarios schematically for the relation between the viscoelasticity behaviour and damping factor.
Phase angle 0 < 𝛿 < 45 𝛿 = 45 45 < 𝛿 < 90 Behaviour Elastic dominated Transitional Viscous dominated
G’ and G’’ G’ > G’’ G’ = G’’ G’ < G’’
Table 4 The given categories of viscoelastic material obtained by an oscillatory measurement [27]
For any ideally viscous fluid, the phase angle would be equal to 90 degrees and the Loss modulus would be in charge over the Storage modulus for this particular fluid.
On the other hand, an ideally elastic fluid would result in having the Storage modulus be greater than the Loss modulus for the fluid, as well as the phase angle would be equal to zero.
In the middle ground between the mentioned cases, the phase angle would be 45 degrees and the Loss modulus, and the Storage modulus will be equal as the fluid has a transitional behaviour as the table 4 states. [28] [27]
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3.3.1. OSCILLATORY AMPLITUDE SWEEP TEST
The basic principle of an oscillatory amplitude sweep test is to keep the frequency constant throughout the test, while the amplitude of the oscillations is varying. Additionally, the temperature of the selected fluid is also kept constant.
The subjected fluid sample will undergo a deformation in form of the applying strain to it.
Although, the internal structure of the fluid does not alter during the deformation.
Parameters such as the Loss modulus and the Storage modulus will be generated with nearly constant values in unique levels as a linear horizontal range will be produced on graph of the test. The range is better known as Linear Viscoelastic Range, LVER, and is presented in the following figure 6. This horizontal range on the graph is solely achieved under the lower amplitudes of oscillations. However, if the applying oscillations have higher amplitudes, the strain will be higher which leads into a critical point where the internal structure will undergo an irreversible deformation. The deformation of the internal structure is represented as the Linear Viscoelastic Range changes from the constant horizontal graph into a nonlinear viscoelastic range. In the end, the Oscillatory Amplitude Sweep test can offer determination of parameters such as flow point and yield point of the sample fluid due to the resulting data and graph.
The flow point of the fluid can be described as the point where the fluid has the ability to start to flow, and the parameter can be determined where Storage modulus and Loss modulus is equal. Graphically, the determination of the flow point can be found as these curves of the modulus crosses each other. As mentioned earlier, the behaviour of the fluid at this point is transitional which means that the phase angle is 45 degrees as well as the 50/50 behaviour regarding viscosity and elastic.
While the flow point can be found where the curves crosses each other, the yield point can be determined graphically where the curves of the Loss – and Storage modulus begins to alter from the horizontal plateau.
